Atoms and Molecules Flashcards
what is the definition of an element?
a substance that cannot be broken down into other substances by chemical reaction
what is the definition of a compound?
a substance consisting of 2 or more different elements combined in a fixed ratio
what atoms make up 96% of all living matter?
C, O, H and N
what is the definition of an atom?
the smallest unit of an element that retains the chemical properties of the element
when do electrons have the greatest potential energy?
the further away from the nucleus they are
what dictates the chemical behavior of an atom?
the no. valence electrons
what are the names and order of shell orbitals ?
1s, 2s, 2p(3), 3s, 3p(3), 3d(5)
what are the strongest chemical bonds?
covalent and non-aqueous ionic bonds
what is the definition of a covalent bond?
the sharing of a pair of valence electrons by 2 atoms
what makes a polar covalent bond?
the differences in the electronegativities between two atoms in a covalent bond
what makes an ionic bond?
where one atom strips valence electrons from its partner, due to its strong electronegative force, that create two ions that can then join together.
what is the name of a positive ion?
cation
what is the name of a negative ion?
anion
what makes a crystal?
an aggregate of cations and anions bound by electrical attraction and arranged in a 3D lattice
does an ionic compound consist of molecules?
no
what does a covalent compound consist of?
molecules having a definite size and number of atoms
what is an example of an ionic molecule?
NH4Cl
why is hydrogen bonding important?
unique properties of water structure of proteins structure and function of DNA structure and function of polysaccharides binding of substrates and enzymes binding of hormones to receptors matching mRNA and tRNA
what are Van der Waals forces?
weak interactions caused by an uneven distribution of electrons in the shells.
what is an example of Van der Waals forces?
geckos feet with van der waals forces with the molecules of smooth surfaces allowing them to stick
why are molecular shapes important?
recognising and bonding with each other e.g. receptors
t/f all chemical reactions are theoretically reversible?
true
how do drugs work?
non-human compounds share molecular shapes with natural compounds
